The invention relates to a breaking device for a multipole electrical circuit breaker with a molded insulating case housing an operating mechanism coupled to a switching bar to provide closing and opening of all the circuit breaker poles, each pole comprising :
a pair of fixed current-conducting terminals, bearing on the base of the case,
an arc extinguishing chamber disposed above the first terminal, and comprising a stacking of metal arc deionization plates, each plate having a V-shaped notch,
a multiple contact system having a plurality of identical movable main contacts, divided into two sets of the same number on either side of a movable arcing contact extending longitudinally according to the center line of the pole, said contacts being pivotally mounted on an axis of a support tunnel securedly united to the bar, and cooperating with corresponding stationary contacts fixed on the internal end of the first terminal, the length of the movable arcing contact being greater than that of each movable main contact,
and a pair of lower and upper arcing horns surrounding the stacking of arc extinguishing chamber plates, the lower arcing horn being securedly united to the upper face of the first terminal with an insulating shield interposed.
The arc forms in the arcing contact separation area located along the center line of the pole, and then develops in the central area of the chamber. Absorption of the arc energy takes place mainly in this area, and the arc remains centered until it is extinguished. In some breaking cases, the hot surfaces of the central area oppose total deionization of the arc, and it is then necessary to increase the number or the surface of the plates to the detriment of the dimensions of the extinguishing chamber.
The object of the invention is to improve the breaking performances of a high-rating multipole circuit breaker.